This invention relates to a supporting arrangement for replaceable cutting inserts for use in cutting tools for metal machining in milling, drilling and turning operations.
A major problem in the design of cutting tools in which a replaceable cutting insert is retained in an insert pocket, is the accuracy with which the location of an operative cutting edge of the cutting insert can be determined. For cutting inserts that are generally square, rectangular or diamond shaped, the insert pocket has an overall corresponding shape and comprises a base support wall and two adjacent side support walls that extend generally perpendicular from the base support wall. Since insert pockets are machined in the toolholders the surface flatness of the support walls of the insert pocket are sufficiently accurate. On the other hand, cutting inserts are not always produced with the same degree of accuracy as the insert pockets. This is particularly true for cemented carbide inserts for metal cutting that are made by pressing and sintering carbide powders. During the sintering process the cutting inserts shrink in a manner that is not absolutely determinable. In other words the cutting inserts become distorted to a certain degree and the surfaces of the sintered cutting insert will generally not have the required flatness. Since three adjacent surfaces, two side surfaces and a bottom surface, of the cutting insert, abut the side support walls and the base support wall of the insert pocket, the accurate location of the cutting insert in the insert pocket and consequently that of the operative cutting edge, will be dependent on the degree of flatness of the surfaces of the cutting insert.
One approach used to solving the problem of the accurate determination of the location of the operative cutting edge is to grind the insert surfaces. Another approach used is to design the insert pocket with three support points on the base support wall, two support points on one of the two adjacent side support walls and one support point on the other one of the two adjacent side support walls. It will be appreciated by those skilled in the art that the use of the term xe2x80x9csupport pointxe2x80x9d does not imply a geometrical point having no dimension, but rather a physical point which will have a small area, the size of which is to be determined by the accuracy required.
Yet another approach used is to design the insert so that the support points are provided on the insert surfaces, instead of on the support walls of the insert pocket. This approach is particularly attractive because it is more cost effective than the other approaches. On the one hand, it does not require grinding of the insert surfaces and on the other hand it requires less machining operations when producing the insert pocket. In applying the third approach two methods have generally been used. In one method, flat and coplanar support surfaces are used, see for example U.S. Pat. No. 5,441,370, and in the other rounded projections are used, see for example U.S. Pat. No. 6,126,366. The former has a disadvantage in that the support surfaces still require a high degree of surface flatness in order to well define the location of the operative cutting edge. The latter has a disadvantage in that the rounded projections form, what is referred to in the art as, undercuts. This means that the latter can only be produced with split die tool sets.
It is an object of the present invention to provide a cutting insert with a support arrangement, with a view to the elimination of the above-mentioned disadvantages, so that when the cutting insert is mounted in a cutting tool, it will be statically retained by a well defined three-point support arrangement and have an accurately located operative cutting edge.
In accordance with the present invention there is provided a replaceable cutting insert for use in a cutting tool comprising:
a top surface, a bottom surface and a plurality of side surfaces extending between the bottom and top surfaces, each side surface intersecting with the top surface at a top edge at least a section of which constitutes a cutting edge;
a plurality of corner side surfaces, each side surface extending between a first corner side surface and a second corner side surface;
a recess in at least side surface, the recess being located below the top edge and having a first and second opposing side edges and an upper edge therebetween;
first and second minor side surfaces adjacent each recess, at least a portion of the first minor side surface extending from the first side edge to the first corner side surface, and at least a portion of the second minor side surface extending from the second side edge to the second corner side surface, wherein the at least a portion of the first minor side surface and the at least a portion of the second minor side surface are flat and non-coplanar, and wherein the at least a portion of the first minor side surface extends outwardly from the first corner side surface to the first side edge and the at least a portion of the second minor side surface slope outwardly from the second corner side surface to the second side edge.
In accordance with a preferred embodiment of the present invention, the first and second minor side surfaces each have a portion bordering on the upper edge of the recess.
Further in accordance with a preferred embodiment of the present invention, the first and second minor side surfaces slope outwardly from the bottom surface toward the top surface.
Further in accordance with a preferred embodiment of the present invention, the first and second minor side surfaces are identical.
In accordance with a preferred embodiment of the present invention, the cutting insert has four side surfaces.
Further, in accordance with a preferred embodiment of the present invention, the each of the four side surfaces is provided with a recess.
In accordance with a specific application of the present invention, the side surfaces of the plurality of side surfaces are identical.
If desired, the first and second minor support surfaces are ground.
The is also provided in accordance with the present invention, a cutting tool having an insert pocket with the cutting insert in accordance with the present invention retained therein, wherein
the insert pocket comprises a base wall, and adjacent rear and side walls extending generally upwardly from the base wall, the rear and side walls being provided with rear and side contact edges, respectively, one of the rear or side contact edge abutting the cutting insert at first and second abutments points located on the first and second side edges, respectively, of the recess in the at least one side surface of the cutting insert.
In accordance with a preferred embodiment of the present invention, the cutting insert has four side surfaces.
Further, in accordance with a preferred embodiment of the present invention, the each of the four side surfaces is provided with a recess and the rear contact edge abuts the cutting insert at first and second abutments points located on the first and second side edges, respectively, of one side surface and the side contact edge abuts the cutting insert at a third abutment point located on the first side edge of an adjacent side surface.
It will be appreciated, that in accordance with this preferred embodiment the cutting insert is retained in the insert pocket by a three-point support arrangement.
In accordance with a specific application of the present invention, the side surfaces of the plurality of side surfaces are identical.
In accordance with a preferred embodiment of the present invention, the first and second minor side surfaces each have a portion bordering on the upper edge of the recess.
Further in accordance with a preferred embodiment of the present invention, the first and second minor side surfaces slope outwardly from the bottom surface toward the top surface.
If desired, the first and second minor support surfaces are ground.